I've smelled an odd smell last week when driving in the country, and it was very foggy. Northern Illinois. I thought perhaps it was chicken manure having been spread on the fields, but I didn't recall the chicken manure smelling quite like that. We sometimes used it when the neighbors cleaned out their chicken barns. It was definitely not pig or cattle manure. ( I grew up on a farm) But it wasn't a smell that was familiar, so it puzzled me.